Bipolar operational power supply

ABSTRACT

A bipolar operational power supply is constructed to provide stable operation over a wide range of gain settings including zero and with various load conditions in order to provide power output with AC or DC control or combinations of the two and in either voltage or current modes.

United States Patent 72 1 Inventor Sarkis Nercossian [56] ReferencesCited a Island UNITED STATES PATENTS [21] P 7963 2,281,238 4 1942Greenwood 330 99 [22] Flled Dec. 30, 1968 2,860,195 1 H1958 Stanley330/20X [45] Patented May 25, 1971 Assi nee Forbro n Co 3,010,08711/1961 Ebbe et a1 330/20X 8 New York ,ff 3,058,068 10/1962 Hinrichs etal.. 330/1 10ux 3,092,783 6/1963 Krohn 330/118X 3,167,718 1/1965 Daviset a1. 330/110UX Primary Examiner-William H. Beha, Jr. 54 BIPOLAROPERATIONAL POWER SUPPLY Barber 7 Claims, 7 Drawing Figs. I [52] US. Cl330/99, ABSTRACT: A bipolar operational power supply is con- 323/19,330/9, 330/ l 9, 330/81 structed to provide stable operation over a widerange of gain [51] Int. Cl H03! H34 settings including zero and withvarious load conditions in [50] Field of Search 330/99, 20, order toprovidepower output with AC or DC control or combinations of the two andin either voltage or current modes.

503 C51 16 1a 49 52 53 l PUSH-PULL POWER 6 AMPLIFIER 21 2s a ePATENIEUMAY S Ian SHEET 1 BF 5 M 503. E5| l8 49 PUSH-PULL POWERAMPLIFIER AMPLIFIER 4:

FIG

INVI'INTOR.

SARKIS NERCESSIAN lOO FIG 2 ATTORNEY PATENTED M25197:

SHEET 2 UF 5 PUSH-PULL POWER AMPLIFIER PUSH-PULL POWER AMPLIFIERINVENTOR. H6 4 SARKIS NERCESSIAN ATTORN EY PATENTED M2 19" 358 1 224 sum3 OF 5 ff J-n/ Y 1 PUSH-PULL POWER AMPLIFIER k 9 INVENTOR.

SARKIS NERCESSIAN BY ATTORNEY PATENIEDHAY25|97| 3581.224

SHEET l 0F 5 4 VOLTAGE PUSH-PULL POWER as AMPLIFIER AMPLIFIER LOAD a420' I I P IF r55 PUSH-PULL. VOLTAGE POWER AMPL'F'ER AMPLIFIER u M W b a?FIG 6 INVENTOR.

SARKIS NERCESSIAN BY WWW ATTORNEY PATENTEUHAYZSIBYI 3.581.224

SHEET 5 0F 5 7 4 /38 VOLTAGE pusu-puu. AMPLIFIER POWER LOAD 6 AMPEFIER#l SLAVE 24 I la i )2 PUSH-PU POWER LOAD -59 AMPEIFIER *2 MASTER m 1INVENTOR.

Fl 6 7 SARKIS NERCESSIAN ATTORNEY BIPOLAR OPERATIONAL POWER SUPPLYBACKGROUND OF THE INVENTION 1. Field of the Invention The presentinvention may be considered as belonging in cascaded amplifiers'withsignal feedback.

2. Description of Prior Art Regulated power supplies have been builtusing control circuits which simulate a control bridge as described inU.S. Pat. No. 3,028,538. Such power supplies have been interconnected ina variety of series and parallel combinations as described in US. Pat.No. 3,275,927. These power supplies may be programmed in various waysgenerally providing unipolar output power. This one commoncharacteristic, however, limits these prior art devices i.e. theirbasically unipolar nature. Because of this unipolar limitation the priorart power supply have been of very little use as bipolar devices.

SUMMARY In accordance with the present invention a high gaindifferential amplifier which is made unconditionally stable is combinedwith a unity voltage gain power amplifier to provide a power supplyhaving novel gain-control capabilities. Two principal feedback paths areemployed. One of these paths is an AC feedback path around the high gainamplifier and including integrating means and the other is a DC feedbackpath around the entire circuit from a power output point to the input ofthe high gain amplifier.

The power supply of the present invention is suitable as a source ofbipolar DC power controlled as to voltage or current, and responsive toslewing rates to a predetermined frequency of several kilocyc'les, or asa hybrid device providing-AC with a DC offset. One of the more importantresults is that its output can be varied from maximum down to zero bymeans of the overall output control without causing instability in thesystem. Other advantages of the present invention will be apparent fromthe detailed description given in connection with various figuresof theDrawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a simplified circuit partlyin block fon'n of one form of the present invention.

FIG. 2 is a graphical representation of the frequency response of theform of the invention shown in FIG. 1.

FIG.. 3 is a simplified circuit partly in block form of a modified formof the present invention.

FIG. 4 is a simplified circuit partly in block fonn of a furthermodified form of the present invention.

FIG. 5 is a simplified circuit partly in block form of a form of thepresent invention adapted to provide regulated current output.

FIG. 6 isa simplified circuit partly in block form of a form of thepresent invention adapted to combine two devices in accordance with thepresent invention and supplying a common load.

FIG. 7 is similar to FIG. 6 except the circuit is adapted to supplypower to two independent loads,

FIG. I is a simplified schematic circuit diagram, partly in block form,of one form of the present invention. Voltage amplifier 1 includes inputterminal 2, common terminal 3 and output terminal 4. Amplifier 1 isbipolar i.e. it accepts positive and negative input voltages or currentsand provides bipolar output voltages. Following amplifier 1, unityvoltage gain push-pull power'ampiifier 5 is provided with input terminal6 and output terminals 7 and 8 in turn connected to load terminals l0and 11 respectively across which is connected load 9. An input controlsignal 12 is connected between common terminal 3 over lead 13 and inputterminal 2 through input resistor l4 and resistor 47. Two feedbackcontrol circuits are provided, one across voltage amplifier 1 in theform of an AC path provided by one of capacitors 15 and 16 selected byswitch 17-18-19 connected from output 4 to input 2, and the other a DCpath across the entire circuit from the output of push-pull poweramplifier 5 to input of voltage amplifier 1 through resistor 47 in theform of variable output control resistor 20 connected from load terminal10 to input terminal 2. Both the AC and DC feedback paths must bedegenerative. This is the case when amplifier 1 inverts between inputterminal 2 and output terminal 4 and amplifier 5 does not invert. The DCfeedback path comprises a variable resistor and serves to control theoutput voltage. The AC feedback path through either of capacitors 15 or16 may be selected by switch 17-18-19 and acting with resistor 47connected between input terminal 2 and null junction 48 serves todetermine the roll-off characteristics of amplifier 1 and furthermore ofthe entire amplifier since power amplifier 5 is chosen to be flat beyondany chosen unity gain frequency. The selection of the AC feedbackimpedance, while generally made in view of the nature of the loadimpedance, is quite independent thereof. A lower impedance in thisfeedback path results in greater tolerance in output voltage or shuntcapacitance while maintaining unconditional stability while a higherimpedance provides higher slewing rate capability. Checking and/orcalibration of the power supply may be accomplished by connecting avoltage determined by the position of variable contact 21 onpotentiometer 21-22 connected between voltage sources 23 and 24 by meansof switch 25-26 through input resistor 27 to input terminal 2. Thesevoltage sources may also be used as sources of input current to programthe output of the power supply.

The frequency response of amplifier 1 as determined by one of capacitorsI5 and 16 and resistor 47 will have a falling characteristic, falling atthe rate of 20 db. per octave, meeting the criteria for stability, andwill have a unity gain frequency at the frequency where the reactance ofthe capacitance (15 or 16) equals the resistance of the resistor 47.Since amplifier 5 is chosen to be essentially flat unity voltage gain atleast to the chosen unity gain frequency, the overall response frominput terminal 48 tooutput terminal 10 will be determined by the chosenresponse of amplifier -I. This mode of operation permits the connectionto any type of load, resistive, inductive or capacitive withoutaffecting the stability of the power supply. Particularly important in apower supply is the ability to vary the output voltage by varying thevalue of the voltage control resistor 20 without affecting the responseor stability of the system. The circuit of the present invention asshown here in FIG. 1 provides stable operation as resistor 20 is varieddown even to zero, providing zero output.

FIG. 1 also shows a safety means for preventing over-driving the outputvoltage. This circuit is particularly significant due to the fact thatamplifiers I and 5 may be operated from different bias voltage sourcesand when heavy current is being drawn from amplified 5, the associatedbias voltages may drop while those supplying amplifier 1 will be at fullvoltage. Under such conditions amplifier 1 may drive amplifier 5 intosaturation. The two back-to-back Zener diodes 49-50 and 51-52 areconnected over leads 53 and 54 between output point 4 of amplifier 1 tonull junction48. Any tendency for the voltage at output 4 to exceed theZener voltages in either direction will cause heavy feedback current toflow preventing any further rise of voltage.

FIG. 2 is a graphical representation in terms of frequency response ofone possible effect of switching between capacitors 15 and 16 of FIG. Isubstantially unaffected by the output voltage or current as determinedby the particular value of output control resistor 20. Curve A is atypical frequency response of amplifier l. for the lower capacitancevalue of capacitances l5 and 16 while curve B is typical for the highervalue. For example, the 400 kHz. unity gain point may be provided withcapacitor 16 equal to I00 pf. and resistor 47 equal to 4 k. ohms, sincethe reactance of I00 pf. is 4 k. at 400 kHz. Increasing the capacitance10 times to 1000 pt. will provide the 40 kHz. unity gain point.

FIG. 3 is a simplified schematic circuit diagram partly in block form ofa modified form of the present invention. The same numbers as those usedin FIG. 1 are used to designate corresponding circuit components. InFIG. 3 a circuit is shown for providing simultaneous AC and DC poweroutput or, stating it another way, an AC output superimposed on a DCoutput. In this case a DC programming voltage supplied as frompotentiometer 2l-22 is applied through closed contacts 25-26 andresistors 27 and 47 to input 2 and in parallel an AC input from ACsource 12 through resistor 14 to null junction 48. The actual outputvoltage components will be equal to the voltages of sources 12 and 21multiplied by the ratio of the resistances of resistors 20 and 14 forsource 12 and 20 and 27 for source 21.

FIG. 4 is a simplified schematic circuit diagram partly in block form ofa further modified form of the present invention. In this form of theinvention both AC (from 12) and DC (from 21-22) are applied to inputterminal 2 through resistor 47. However, in this case the output acrossload 9 is controlled by a remote output control resistor 28 connectedbetween load terminal 10 and input terminal 2 over a remote lineshielded cable shielded by grounded shield 29. Otherwise the operationis similar to that of FIG. 3 described above.

FIG. is a simplified schematic circuit diagram partly in block form forproviding a regulated output current to the load. In this form of theinvention the output control resistor 28 is connected from junctionpoint 30 to input terminal 2. A

. current sensing resistor 29 is connected in series with load resistor9 so that output current from amplifier 5 flowing in load resistor 9also flows through resistor 29. The voltage drop in resistor 29 due tothis output current supplies the voltage applied through resistor 28back to input 2. The voltage across load 9 is thus current regulatedrather than voltage regulated as in FIGS. 1, 3 and 4.

FIG. 6 is a simplified schematic circuit diagram partly in block form ofa form of the present invention in which two of the bipolar powersupplies as described above are connected to cooperate in supplying acommon load. The numerical designations are the same for partscorresponding with parts as described above and in the second powersupply corresponding parts are designated by the same numbers primed.The upper power supply is provided with a programming voltage fromadjustable contact 21 of potentiometer 21-22 bridged across voltagesources 23 and 24. The reference resistor is 27 and the output voltagecontrol is variable resistor 20 connected between load terminal 32 andinput terminal 2 over lead 33. Similarly, the second power supply isprovided with programming voltage from adjustable contact 21' ofpotentiometer 21 '-22' bridged across voltage sources 23' and.

24'. The reference resistor is 27' and the output voltage control isvariable resistor 20' connected between output terminal 7' and inputterminal 2' over lead 36. The load 31 is connected between terminals 32and 34 and the two power supply output tenninals 11 and l0'11' areconnected in series across these load tenninals so that the sum of theoutput voltages of the two power supplies are applied across the load,The voltage control feedback circuit connected over lead 33 to loadterminal 32 and the return circuit over leads 35-37 connected to loadterminal 34 provides for remote sensing of the load voltage so that anyvoltage drops in leads between power supply output terminals 10 and 11and load terminals 32 and 35 respectively are outside the voltagecontrol circuit and the actual lo'ad voltage is regulated unaffected bythe lead drops. It will be seen that the two power supplies willcontribute equally to the load voltage if the two input voltages,reference resistors and voltage control resistors are made equal andwill contribute unequally otherwise.

FIG. 7 is a simplified schematic circuit diagram partly in block form ofa form of the invention similar to that of FIG. 6 in that two powersupplies are involved but differing in that separate loads are powered.In FIG. 7 the lower power supply is programmed by potentiometer output21 and supplies power to load 39 while the upper power supply isprogrammed by the output voltage of the lower power supply over leads 45and 46 through input resistor 44. Since the power supply output volta esare inverted from the ingut voltages the output etween ermmals 7 and 8'1s mverte as it IS app red to mput 2. This inversion is accomplished byconnecting terminal 7 to terminal 8 and deriving the input for the upperpower supply from terminal 8'.

Iclaim:

1. In a bipolar output regulated power supply, the combination of: 1

an operational voltage amplifier including an inverting input terminal,an output terminal and a common terminal;

. a push-pull, unity voltage gain, power amplifier coupled to saidoperational voltage amplifier output terminal and including an inputterminal and two output terminals, one in phase and the other out ofphase with the last said input tenninal;

a null junction terminal;

resistive means connected between said null junction and said invertinginput to the voltage amplifier;

resistive degenerative feedback'means connected between said in phaseoutput and said null junction;

capacitive degenerative feedback means connected between said output ofthe voltage amplifier and said inverting input thereof;

and a source of input voltage connected through a resistive meansbetween said common terminal of the voltage amplifier and said nulljunction; whereby the unity gain frequency of said voltage amplifier issubstantially determined by the capacity of said capacitive means andthe resistance of said first said resistive means. V

2. A bipolar output regulated power supply as set forth in claim 1; I

wherein said resistive feedback means is a variable resistor forcontrolling the output of said power supply.

3. A bipolar output regulated power supply as set forth in claim 1;

and including two back-to-back series connected Zener diodes connectedbetween said in phase output of said power amplifier and said nulljunction for limiting the output voltage of said power amplifier in boththe positive and negative direction.

4. A bipolar output regulated power supply as set forth in claim 1;

and including means for applying known voltages, both positive andnegative, through resistive means, between said common terminal of saidvoltage amplifier and said null junction, for activating said powersupply in a known mode.

5. A bipolar output regulated power supply as set forth in claim 1; andincluding a source of known DC current connected between said commonterminal and said null junction and wherein said source of input voltageis a source of alternating current.

6. A bipolar output regulated power supply as set forth in claim 1;wherein said capacitive feedback means is plural and including switchmeans for selecting one of said capacitive means to be active connectedbetween said output of said voltage amplifier and said inverting inputthereof.

7. A bipolar output regulated power supply as set forth in claim 1;wherein said power amplifier has a frequency response which issubstantially fiat to and beyond said unity gain frequency of said poweramplifier.

1. In a bipolar output regulated power supply, the combination of: anoperational voltage amplifier including an inverting input terminal, anoutput terminal and a common terminal; a push-pull, unity voltage gain,power amplifier coupled to said operational voltage amplifier outputterminal and including an input terminal and two output terminals, onein phase and the other out of phase with the last said input terminal; anull junction terminal; resistive means connected between said nulljunction and said inverting input to the voltage amplifier; resistivedegenerative feedback means connected between said in phase output andsaid null junction; capacitive degenerative feedback means connectedbetween said output of the voltage amplifier and said inverting inputthereof; and a source of input voltage connected through a resistivemeans between said common terminal of the voltage amplifier and saidnull junction; whereby the unity gain frequency of said voltageamplifier is substantially determined by the capacity of said capacitivemeans and the resistance of said first said resistive means.
 2. Abipolar output regulated power supply as set forth in claim 1; whereinsaid resistive feedback means is a variable resistor for controlling theoutput of said power supply.
 3. A bipolar output regulated power supplyas set forth in claim 1; and including two back-to-back series connectedZener diodes connected between said in phase output of said poweramplifier and said null junction for limiting the output voltage of saidpower amplifier in both the positive and negative direction.
 4. Abipolar output regulated power supply as set forth in claim 1; andincluding means for applying known voltages, both positive and negative,through resistive means, between said common terminal of said voltageamplifier and said null junction, for activating said power supply in aknown mode.
 5. A bipolar output regulated power supply as set forth inclaim 1; and including a source of known DC current connected betweensaid common terminal and said null junction and wherein said source ofinput voltage is a source of altErnating current.
 6. A bipolar outputregulated power supply as set forth in claim 1; wherein said capacitivefeedback means is plural and including switch means for selecting one ofsaid capacitive means to be active connected between said output of saidvoltage amplifier and said inverting input thereof.
 7. A bipolar outputregulated power supply as set forth in claim 1; wherein said poweramplifier has a frequency response which is substantially flat to andbeyond said unity gain frequency of said power amplifier.